The Efficacy of Blood Flow Restriction Training to Improve Quadriceps Muscle Function after Anterior Cruciate Ligament Reconstruction.

BACKGROUND: Blood flow restriction training (BFRT) is a popular rehabilitation intervention after anterior cruciate ligament reconstruction (ACLR). However, there are a lack of clinical trials establishing the efficacy of using BFRT during rehabilitation to improve quadriceps muscle function. PURPOSE: The purpose of this study is to evaluate the efficacy of blood flow restriction training to improve quadriceps muscle strength, morphology, and physiology, and knee biomechanics in individuals after ACLR in a double-blind, randomized, placebo-controlled clinical trial (NCT03364647). METHODS: Forty-eight athletes (20 females/28 males) were randomly assigned to low-load strength training with active BFRT or standard of care strength training with a sham unit. Treatment occurred for 1-month pre-surgery and 4 to 5 months post-surgery with both groups following the same standard rehabilitation protocol. Outcome variables were measured at baseline and 4 to 5 months post-surgery. Quadriceps muscle strength (isometric and isokinetic peak torque and rate of torque development) was measured on an isokinetic dynamometer. Quadriceps muscle morphology (physiological cross-sectional area, fibrosis) was determined using magnetic resonance imaging. Quadriceps muscle physiology (fiber type, fiber cross-sectional area, satellite cell abundance, collagen content, fibrogenic/adipogenic progenitor cells) was evaluated with muscle biopsies of the vastus lateralis. Knee extensor moment and knee flexion angle were measured via three-dimensional gait analysis. Change scores were calculated as: post-intervention - baseline. Two-sample t -tests were then used to assess between-group differences for each outcome variable. RESULTS: No significant between-group differences were found for any outcome variable. CONCLUSIONS: The addition of BFRT to a rehabilitation program for athletes pre- and post-ACLR was no more effective than standard rehabilitation for improving quadriceps muscle function. Clinicians should consider the value of BFRT relative to the cost, time, and discomfort for patients in light of these results.